Ontogeny of auditory saccular sensitivity in the plainfin midshipman fish, Porichthys notatus

Abstract

The auditory system of the plainfin midshipman fish, Porichthys notatus, is an important sensory receiver system used to encode intraspecific social communication signals in adults, but the response properties and function of this receiver system in pre-adult stages are less known. In this study we examined the response properties of auditory-evoked potentials from the midshipman saccule, the main organ of hearing in this species, to determine whether the frequency response and auditory threshold of saccular hair cells to behaviorally relevant single tone stimuli change during ontogeny. Saccular potentials were recorded from three relative sizes of midshipman fish: small juveniles [1.9-3.1 cm standard length (SL), large juveniles (6.8-8.0 cm SL) and non-reproductive adults (9.0-22.6 cm SL)]. The auditory evoked potentials were recorded from the rostral, middle and caudal regions of the saccule while single tone stimuli (75-1,025 Hz) were presented via an underwater speaker. We show that the frequency response and auditory threshold of the midshipman saccule is established early in development and retained throughout ontogeny. We also show that saccular sensitivity to frequencies greater than 385 Hz increases with age/size and that the midshipman saccule of small and large juveniles, like that of non-reproductive adults, is best suited to detect low frequency sounds (<105 Hz) in their natural acoustic environment.

Vocal differentiation parallels development of auditory saccular sensitivity in a highly soniferous fish

“…Our findings are in contrast to those reported from a study conducted in the batrachoidid P. notatus, which showed via saccular potential recordings that auditory threshold curves were similar throughout development (Alderks and Sisneros, 2011) (Fig. 4).…”

“…Note that within Lusitanian toadfish, small juveniles differed significantly from large juveniles and adults, which revealed higher auditory sensitivity and produced the full vocal repertoire. In contrast, in the midshipman fish, the auditory sensitivity of different size groups is similar and vocal behaviour has only been detected in adults (based on Alderks and Sisneros, 2011). Number of animals and number of recordings per group are indicated in parentheses.…”

“…anurans, Boatright-Horowitz and Simmons, 1995). Ontogenetic studies of fish hearing show diverse results, ranging from no differences (Popper, 1971;Zeddies and Fay, 2005), to expansion of the detectable frequency range (Higgs et al, 2002(Higgs et al, , 2003Alderks and Sisneros, 2011), up to increases in auditory sensitivity with size/age (Kenyon, 1996;Wysocki and Ladich, 2001;Sisneros and Bass, 2005).…”

Seasonal plasticity of auditory saccular sensitivity in “sneaker” type II male plainfin midshipman fish, Porichthys notatus

“…The procedures for exposing and recording from the inner ear saccule followed those used in previous studies (Sisneros 2007(Sisneros , 2009bAlderks and Sisneros 2011). Briefly, animals were initially anesthetized in a 0.025% ethyl-p-aminobenzoate/saltwater bath until the fish's opercula ceased movement for at least 5 min.…”

“…Recently Popper and Fay (2011) proposed that all future fish hearing studies should independently characterize particle motion and sound pressure sensitivities of fish regardless of any hearing specializations that fish may possess (e.g., accessory hearing structures such as Weberian ossicles that connect the swim bladder to the inner ear). Previous auditory physiology studies of the plainfin midshipman fish have primarily reported auditory responses with regard only to sound pressure Bass 1999, 2001;Sisneros et al 2004;Bass 2003, 2005;Sisneros 2007Sisneros , 2009bAlderks and Sisneros 2011;Rohmann and Bass 2011; but for the exception see Weeg et al 2002). Thus, better characterization of particle motion sensitivity in this species and across the different sexual phenotypes is warranted.…”